Effects of surgical sterilization on the health and society of dogs and cats

The advantages of gonadectomy include the reduction of pathologies of the reproductive tract, reduction of pregnancies and disorders related to childbirth; decrease in hormone-related disorders such as vaginal prolapse in bitches and breast hypertrophy in cats; The disadvantages of gonadectomy include surgical and anesthetic complications, an increased risk of neoplasm affecting other organs, an increased incidence of certain musculoskeletal and endocrinological disorders, obesity and urinary incontinence. Intraoperative and post-surgical complications are generally mild and self-limiting. The reported incidence of surgical complications is 6.1–27% in bitches and dogs and 2.6–33% in queens and cats. Reported short-term complications of OV or OHE include hemorrhage of the ovarian or uterine peduncle, vulvar blood loss, pseudocyst onset, dehiscence or infection of the surgical wound and, very rarely, peritonitis or gutting. Long-term complications of OV or OHE include ovarian residue syndrome, hydroureter and ipsilateral renal dysfunction, uterine or ovarian pedicle granuloma and uterine stump disease. When bitches and cats are sterilized while in estrus, there is a greater risk of bleeding due to the influence of estrogen. Overpopulation of pets can occur due to pet owners who allow irresponsible breeding by adopting wild animals in freedom. Although it has been described that 82% of cats and 64% of dogs in the United States have been spayed, a recent study found that only 52% of people who had purchased a dog or cat in the past year had done so to subject it to gonadectomy. Most people resort to gonadectomy because they cannot tolerate the normal reproductive behaviors of their animals. A concern is related to the training of sterilized dogs, according to some they would be more careful as they are less distracted by behavior related to mating. In rats it has been shown that attention is not influenced by changes in testosterone concentration while it has been observed that it can affect the working memory acuity in space. Gonadectomy can affect aggression. An increase in aggressiveness has been described in both males and females after gonadectomy and in females after OHE; most commonly in women spayed at <1 year of age who showed aggression before surgery. The form of aggression best controlled by castration in both dogs and cats is the fight between males. In a study of older male dogs with mild cognitive impairment, those who were castrated were more likely to develop severe cognitive impairment than those left intact. Androgen deprivation is associated with an increase in amyloid deposition in the brains of humans and rodents and a reduced number of synaptic connections in the brains of rodents and primates. Breast cancer is very common in dogs and cats, with a reported incidence of 3.4 and 2.5%, respectively. Intact dogs and cats are seven times more likely than neutered dogs and cats to develop this neoplasm as they age. A study suggested that breast cancer may be more common in females who have shown more than three episodes of false pregnancy in their life, once again supporting the role of hormonal stimulation of breast tissue as a factor associated with the neoplastic transformation of that tissue. The prostate cancer is rare in dogs, with an incidence of 0.2-0.6% and is always practically malignant; both adenocarcinoma and transitional cell carcinoma are described. Several studies have documented a higher incidence of prostate cancer in castrated dogs, with an increase in risk ranging from 2.4 to 4.3 times. Prostate cancer is extremely rare in cats, but in a study of eight cats with prostate cancer, seven were neutered. The incidence of transitional cell carcinoma is at most 1% of malignant tumors. After gonadectomy, the incidence of transitional cell carcinoma of the bladder and urethra of females and of the urethra of males underwent a 2-4-fold increase in risk. The cause-effect relationship is unclear. Testicular neoplasm is very common in older male dogs, with a reported incidence of 0.9%. Testicular neoplasm is rare in male cats. Castration is curative. The overall incidence of hemangiosarcoma in dogs is 0.2% and in cats 0.03%. The incidence of both splenic and cardiac hemangiosarcoma increased in dogs after gonadectomy; in females, the risk of splenic hemangiosarcoma after OHE increases by a factor of 2.2 and the risk of cardiac hemangiosarcoma increases by a factor of 5, and in male dogs, the overall risk of hemangiosarcoma increases by a factor of 2.4 after castration. Osteosarcoma is an uncommon tumor with a total incidence of 0.2%. The incidence increased with gonadectomy by a factor of 1.3–2 with no clear cause-effect relationship. From a dermatological point of view, an increase in the incidence of mast cell tumors has been observed in sterilized bitches although the cause-effect correlation is unclear. The ossification of the growth cartilages is mediated by gonadal hormones. Physical closure has been shown to be delayed in dogs and cats neutered or neutered in prepubertal age. A large study found an increase in the incidence of hip dysplasia in young dogs spayed. A hypothesis of these results is the asymmetry in the closure of the physiques which causing deformity and laxity of the hip joint would cause arthritis. After gonadectomy, anterior cruciate ligament rupture is also more frequent. Estrogen-reactive urinary incontinence is much more common in neutered dogs with a reported incidence of 4.9-20.0%. Another factor contributing to the manifestation of this pathology is a body weight greater than 20 kg. The incidence of pyometra in dogs left intact is high, approximately 24–25% within 10 years. Pyometra also occurs in cats. Benign prostatic hyperplasia is very common in elderly dogs, with an reported incidence of 50% by 2.4 years of age and 75-80% in dogs aged 6 years and over. Castration is curative. Multiple studies have failed to show correlation between castration, urethral diameter and incidence of urinary tract obstruction in male cats. Similarly, without clear clinical significance, castrated dogs at <7 weeks of age had reduced penile diameter, size and radio density of the penile bone accompanied by immature preputial development compared to male dogs castrated at 7 months of age or left intact. There have been no reports of an increase in adrenal disease in populations of cats and dogs secondary to gonadectomy. Cats have a 2 to 9-fold increased risk of developing diabetes mellitus after sterilization, one hypothesis is that this is due to reduced insulin sensitivity. From a study on castrated beagle dogs and whole males, there were no changes in resting serum TSH, thyroxine concentrations or changes in the stimulation test. In retrospective studies, up to 2.8% of the canine population has been shown to be obese, of which 50% are gonadectomized dogs and cats. Castrated cats show an increase in serum concentrations of IGF-1 (insulin-like growth factor), prolactin and leptin, all involved in fat metabolism. Most studies evaluating lifespan suggest that castrated animals live longer than intact animals.